#prr

She turned in time to see a new shape burst out from under the island’s shadow, a shiny blur of polished brass and whirring rods, gunning gamely for the yard’s throat.

It was a smaller engine than the first, painted in neat polished black with red and white lining. The cylinders were small and boxy, set behind the wheels of the leading axle. With each breath from the chimney, a great snort of steam would burst from one of them, or from beneath, between the frames; peering closer, she could see the outline of a massive third piston-housing under the smokebox, half-hidden by pilot beam and cowcatcher.

Neat valances covered two sets of large driving wheels, the rear one eclipsed by the cab side-walls, while a complicated set of polished steel rods whirled below. And above, on the leading wheel-arch, polished to the same brassy sheen as whistle, bell, and safety-valves, was a gracefully-curved nameplate:

Dreadnought.

What this is all describing is an LNWR Dreadnought-class 2-2-2-0 Webb Compound. One of these (No. 1320) was actually exported to the Pennsylvania Railroad in the U.S. and ‘Americanized’. The fictional Dreadnought will have been through a similar process.

Dreadnought is sapient, with a "Coal Heart" in her firebox which acts as the mind and main power source for the loco (though she still consumes coal).

A real LNWR Dreadnought. Note the large shiny round disk below the smokebox door, mostly hidden under the frames--that's the low pressure cylinder.

the real life PRR 1320 'Pennsylvania', the exported Webb Compound, with an airbrake compressor, a cowcatcher, a bell, headlamp, and larger cab.

The first iteration of my sketch of Dreadnought, from the evening of June 1st. Pretty rough--a lot of the proportions hadn't been figured out quite yet.

The next morning at around 10:30 AM, I began work again.

She briefly had a more american outline boiler, but I got rid of it.

Even after a lot of tweaking, the proportions still didn't look right. It turned out that the spacing between the drivers was totally wrong.

After much surgery--cutting up the boiler, moving the wheels, and stitching the lines back together--the locomotive was looking a lot more authentic.

The sketch was finished by 1:42 PM.

By 3:40, the locomotive and tender bodies were clean lined.

I was running out of time before a meeting as I was putting the wheels on.

The Joy Valve Gear turned out to be really easy to draw, almost disappointingly so.

Joy Valve Gear takes the valve timing from the connecting rod, rather than the drive wheel or axle.

So at 5:00, before I left for my meeting, this was the state of the drawing.

and, um, I also may have sketched it with pencil during the meeting...

I didn't draw any more that night, but at 9:50 AM this morning, I got back to work.

The tender trucks are off of NYC 999, which have this really weird suspension with those inverted leaf springs. The tender is also a little longer to accomodate.

At 10:15 AM, the clean line art was finished:

Coloring then took until about 1:00 PM. There's a lot of very fine line work and there's only so many shortcuts that can be taken. The livery is based on the LNWR lined black (which is extremely similar to BR Black), but with the white wall tires off of NYC 999 (since the tender trucks looked wrong without them and the loco looked wrong with them on just the tender). There's also a white roof, just because.

The shading was done with black for the shadows, and cool grey for the highlights. British steam engines were usually kept pretty shiny anyway, but this locomotive is kept in very good condition by its owner

the full drawing (shown in the OP) was finished at 2:43 PM. But I also made some variants, like the transparency shown above, the solid color version that's brightened for a white/transparent background. (also shown above), and the following:

Transparent with no steam and lights.

background with no steam and lights.

and as before with Featherfoot, a lineless variant. (this isn't a true lineless drawing, it's just the lined drawing without the lines)